In the past, copper or a copper alloy having good electrical conductivity has been used for electrical contact components. As characteristics of contacts have improved recently, pure copper or a copper alloy has been seldom used. Alternatively, products have been developed in which various surface processing is performed on copper or copper alloy. In particular, a noble metal is coated onto an electrical contact region as a material largely utilized for an electrical contact. Among those, noble metals such as Au, Ag, Pd, Pt, Ir, Rh, and Ru have stable property and good electrical conductivity, and are utilized as various electrical contact materials. Especially, Ag exhibits excellent conductivity, and is wildly used in various applications due to a relatively low price.
Recently, an electrical contact material having a good abrasion resistance is used for electrical contacts such as connector terminals and sliding switches for automobile harnesses, contact switches mounted on mobile phones, or terminals for memory cards and PC cards, in which insertion and extraction is repeatedly conducted or a sliding operation is performed. In order to improve the abrasion resistance, contact materials that use hard Ag or hard Au are generally used. In particular, since Ag is less expensive than Au, Pd, etc., a hard gloss Ag plating material has been developed in recent years to use in places where the abrasion resistance is required. Furthermore, a plating and cladding material have been developed, in which micro-particles are dispersed, and various surface processing materials are developed for improving sliding property of a material for an electrical contact.
In order to improve the sliding property, a sealing process or a lubrication process is performed on a surface of a material after plating. For example, after pure Ag plating is applied onto an Ag alloy, an organic film comprised of an aliphatic amine, a mercaptan, or a mixture thereof is provided, thereby improving sulfur resistance and abrasion resistance (refer to Japanese patent publication No. JP 06-212491).